Electrolyte renal regulation

Declining renal function disrupts the homeostasis of the systems regulated by the kidney, leading to fluid and electrolyte imbalances, anemia, and metabolic bone disease. 

The potent antidiuretic hormone AVP orchestrates the regulation of free water absorption, body fluid osmolality, cell contraction, blood volume, and blood pressure through stimulation of three G-protein-coupled receptor subtypes Vi-vascular types a and b, V2-renal, and V3-pituitary. Increased AVP secretion is the trademark of several pathophysiological disorders, including heart failure, impaired renal function, liver cirrhosis, and SIADH. As a consequence, these patients experience excess water retention or inadequate free-water excretion, which results in the dilution of sodium concentrations, frequently manifesting as clinical hyponatremia (serum sodium concentration <135mmol/L). This electrolyte imbalance increases mortality rates by 60-fold. Selective antagonism of the AVP V2 receptor promotes water... 

Kidney Failure, Chronic An irreversible and usually progressive reduction in renal function in which both kidneys have been damaged by a variety of diseases to the extent that they are unable to adequately remove the metabolic products from the blood and regulate the body s electrolyte composition and acid-base balance. Chronic kidney failure requires hemodialysis or surgery, usually kidney transplantation. [NIH]... 

No specific antidote has been shown to be effective in treating 1,2-dibromoethane intoxication once absorption into the bloodstream has occurred (Ellenhorn and Barceloux 1988). Intravenous infusions of glucose may limit the hepatotoxicity of 1,2-dibromoethane (ERA 1989b). During the recovery phase, a diet rich in vitamin B and carbohydrates may limit liver damage (Dreisbach and Robertson 1987 Lawrence and Michaels 1984). Hemodialysis may be needed to regulate extracellular fluid and electrolyte balance and to remove metabolic waste products if renal failure occurs (ERA 1989b). 

Mechanism of Action An electrolyte that is essential for the function and integrity of the nervous, muscular, and skeletal systems. Calcium plays an important role in normal cardiac and renal function, respiration, blood coagulation, and cell membrane and capillary permeability. It helps regulate the release and storage of neurotransmitters and hormones, and it neutralizes or reduces gastric acid (increase pH). Calcium acetate combines with dietary phosphate to form insoluble calcium phosphate. Therapeutic Effect Replaces calcium in deficiency states controls hyperphosphatemia in end-stage renal disease. 

Mineralocorticoids are involved in controlling electtolyte and fluid levels.9,44 The primary mineralo-corticoid produced by the adrenal cortex is aldosterone. Aldosterone increases the reabsorption of sodium from the renal tubules. By increasing sodium reabsorption, aldosterone facilitates the reabsorption of water. Aldosterone also inhibits the renal reabsorption of potassium, thus increasing potassium excretion. Mineralocorticoid release is regulated by fluid and electrolyte levels in the body and by other hormones, such as the renin-angiotensin system. 

The primary function of the renal system is the elimination of waste products, derived either from endogenous metabolism or from the metabolism of xenobiotics. The latter function is discussed in detail in Chapter 10. The kidney also plays an important role in regulation of body homeostasis, regulating extracellular fluid volume, and electrolyte balance. 

Hyponatremia is caused by an excess of total body water relative to total body sodium and can result from a number of underlying conditions, including the syndrome of inappropriate antidiuretic hormone secretion (SIADH), cirrhosis, and congestive heart failure (CHF). In each of these conditions, inappropriate production of arginine vasopressin (AVP) [also known as vasopressin or antidiuretic hormone (ADH)], a neurohormone that regulates renal electrolyte-free water reabsorption, contributes to enhanced renal water retention, leading to decreased serum sodium concentrations.7 Hyponatremia can be characterized as hypervolemic, euvolemic, or hypovolemic... 

In 1989 a renal natriuretic factor (RNF) was detected for the first time and termed urodilatin (P. Schulz-Knappe et at). As examinations have hitherto shown, urodilatin is formed in the medial nephron of the kidney and causes a distad inhibition in the absorption of water and sodium. Its half-life is likewise about 3 minutes. Although ANF is most probably of limited significance for the excretion of sodium and its influence on sodium homoeo-stasis in cases of liver cirrhosis (with or without ascites) has still not been fully clarified, urodilatin is deemed to be important for the regulation of the water and electrolyte balance. (3) (s. tab. 16.5)... 

The therapeutic range and risks associated with under- and overinfusion are highly drug and patient dependent. Intravenous delivery of fluids and electrolytes often does not require very accurate regulation. Low-risk patients can generally tolerate well infusion rate variability of 30% for fluids. In some situations, however, specifically for fluid-restricted patients, prolonged under- or overinfusion of fluids can compromise the patient s cardiovascular and renal systems. 

Olson et al., 2009). The current gold standard parameters are sCr and BUN, which are insensitive and inadequate to detect especially mild to moderate or tfansient renal injury after acute nephrotoxic drug insult (Kellum et al., 2002 Bonventre et al., 2010). Recent studies have demonstrated that inaeased sCr and BUN concentrations may be predictive of kidney injury only when nearly or more than 50% of the functional nephron capacity has been lost and the kidneys are unable to regulate fluid and electrolyte homeostasis (Lameire et al., 2008 Olson et al., 2009 Bonventre et al.,... 

Ruid volume regulation is necessary to maintain life. Decreased and inadequate fluid volume (i.e., hypovolemia) can result in decreased flow and perfusion to the tissues. Increased or excessive fluid volume (i.e., hypervolemia) can placed stress on the heart and cause dilutional electrolyte imbalance. It is clear that the renal system plays a vital role in fluid management. If the kidneys are not functioning fully, fluid excretion and retention will not occur appropriately in response to fluid adjustment needs. 2... 

Similarly, if renal system function is insufficient or nonexistent (failure), reabsorption and excretion of electrolytes may occur without response to the feedback mechanism or consideration of current levels of electrolytes. For example, in renal failure, potassium may be not be excreted and may even be reabsorbed, although the potassium level is already high because there is a failure of the usual feedback mechanism. Table 1-3 is a summary of regulation mechanisms for representative electrolytes. 

The renal system plays an important role in the regulation of fluids and electrolytes and is one of the two major systems involved in restoration of acid-base balance. In addition, the renal system has other vital roles, such as production of erythropoetin needed for red blood cells health, essential for oxygenation of tissues. The primary functions of the renal system are... 

Acute tubular necrosis (ATN), ischemia, and death of renal tubules are the greatest threats to the renal system after a burn injury. Tubular necrosis will result in impairment of renal function and fluid and electrolyte, as well as acid-base, imbalances owing to impaired renal function in regulation of these areas. 

From the above succinct review of the mechanism regulating blood pH, it is clear that acidosis or alkalosis may result from metabolic, renal, or pulmonary dysfunctions. Depending upon the severity of the dysfunction, the electrolyte imbalance will not be associated with severe changes in blood pH (compensated acidosis or alkalosis), or the blood pH may reach values incompatible with survival. 

Hi) regulation of the rate of excretion of electrolytes by the renal system,... 

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